Understanding NEC Article 550: Mobile Homes, Manufactured Homes, and Mobile Home Parks
NEC Article 550 provides safety standards for electrical systems in mobile homes, manufactured homes, and mobile home parks. These requirements address wiring, grounding, equipment installation, and connections to external power supplies, ensuring safety and compliance for temporary or permanent installations.
Scope of Article 550
This article applies to:
- Mobile and Manufactured Homes: Electrical systems within or on these structures, including power connections.
- Mobile Home Parks: Installation of wiring and electrical equipment within parks, up to service conductors or service equipment.
Referenced Standards:
- NFPA 501: Standards for manufactured housing.
- 24 CFR 3280: HUD regulations for electrical systems in manufactured homes.
Key Requirements for Mobile and Manufactured Homes
- Power Supply
- A single 50-ampere supply cord or permanently installed feeder supplies power.
- Supply cords must have a 3-pole, 4-wire, grounding-type plug rated for 50 amperes, 125/250 volts.
- Disconnecting Means
- A disconnecting means must be installed at the point of entrance of the supply cord.
- This equipment must be marked and easily accessible, providing overcurrent protection for all branch circuits.
- Branch Circuits and Receptacles
- Branch circuits for lighting and small appliances must comply with NEC standards.
- Ground-fault circuit-interrupter (GFCI) protection is required in areas like kitchens, bathrooms, and outdoor receptacles.
- Wiring Methods
- Approved wiring methods include nonmetallic cables, jacketed Type MC cables, or metal raceways.
- Wiring under the chassis must be protected by raceways suitable for wet locations.
- Grounding and Bonding
- Metal parts must be bonded to the grounding terminal of the panelboard.
- A grounding electrode conductor connects the electrical system to the service equipment.
Requirements for Mobile Home Parks
- Service Equipment
- Service equipment must be mounted outdoors and within sight of the mobile home.
- Disconnecting means must be installed for individual homes and labeled clearly.
- Distribution Systems
- Distribution systems must supply 120/240 volts to each mobile home lot.
- Demand factors for service and feeder calculations must follow specified NEC guidelines.
- Outdoor Equipment
- Luminaires, outlets, and equipment installed outdoors must be rated for wet or damp locations.
- Additional receptacles for accessory buildings must comply with grounding and bonding requirements.
Testing and Calculations
- Testing
- All wiring must pass dielectric strength, continuity, and polarity tests before installation.
- Load Calculations
- Feeder and branch circuit loads must be calculated to ensure proper ampacity, using demand factors for lighting, appliances, and HVAC equipment.
Applications
NEC Article 550 is essential for ensuring safe electrical systems in:
- Mobile and Manufactured Homes: Temporary and permanent housing.
- Mobile Home Parks: Utility infrastructure and lot-specific connections.
- Accessory Structures: Garages, sheds, or additional buildings.
Conclusion
NEC Article 550 addresses the unique electrical requirements for mobile and manufactured homes and parks, ensuring safety, reliability, and compliance with national standards. Proper grounding, wiring, and testing practices are critical for secure installations.
